Roasting garlic (Washington Post, April 8, 2009)

[L]op off the top of a head of garlic so that its cloves are exposed a bit, drizzle with olive oil, wrap tightly in aluminum foil and toss into the oven with whatever else is baking.

Normally it takes about 40 minutes in a 400-degree oven; you'll know the garlic is ready when you squeeze the foil and it feels soft.